1. Field of the Invention
This invention relates to the use of anti-pancreatic cancer antibodies that bind with high selectivity to pancreatic cancer cells to detect and/or diagnose pancreatic adenocarcinoma, preferably at the earliest stages of the disease. More preferably, antibody-based assays are capable of detecting about 85% or more of pancreatic adenocarcinomas, with a false positive rate of 5% or less for healthy controls. In particular embodiments, the methods and compositions can be used to detect and/or diagnose pancreatic adenocarcinoma by screening serum samples from subjects and preferably can detect 60% or more of stage I pancreatic cancers and 80% or more of stage II cancers by serum sample analysis.
In preferred embodiments, the anti-pancreatic cancer antibody competes for binding to pancreatic cancer mucin with a PAM4 antibody comprising the light chain variable region complementarity-determining region (CDR) sequences CDR1 (SASSSVSSSYLY, SEQ ID NO:1); CDR2 (STSNLAS, SEQ ID NO:2); and CDR3 (HQWNRYPYT, SEQ ID NO:3); and the heavy chain CDR sequences CDR1 (SYVLH, SEQ ID NO:4); CDR2 (YINPYNDGTQYNEKFKG, SEQ ID NO:5) and CDR3 (GFGGSYGFAY, SEQ ID NO:6). Most preferably, the anti-pancreatic cancer antibody is a humanized PAM4 (hPAM4) antibody comprising the light chain CDR sequences CDR1 (SASSSVSSSYLY, SEQ ID NO:1); CDR2 (STSNLAS, SEQ ID NO:2); and CDR3 (HQWNRYPYT, SEQ ID NO:3); and the heavy chain CDR sequences CDR1 (SYVLH, SEQ ID NO:4); CDR2 (YINPYNDGTQYNEKFKG, SEQ ID NO:5) and CDR3 (GFGGSYGFAY, SEQ ID NO:6), along with human antibody framework (FR) and constant region sequences.
2. Related Art
Pancreatic cancer is a malignant growth of the pancreas that mainly occurs in the cells of the pancreatic ducts. This disease is the ninth most common form of cancer, yet it is the fourth and fifth leading cause of cancer deaths in men and women, respectively. Cancer of the pancreas is almost always fatal, with a five-year survival rate that is less than 3%.
The most common symptoms of pancreatic cancer include jaundice, abdominal pain, and weight loss, which, together with other presenting factors, are nonspecific in nature. Thus, diagnosing pancreatic cancer at an early stage of tumor growth is often difficult and requires extensive diagnostic work-up, often times including exploratory surgery. Endoscopic ultrasonography and computed tomography are the best noninvasive means available today for diagnosis of pancreatic cancer. However, reliable detection of small tumors, as well as differentiation of pancreatic cancer from focal pancreatitis, is difficult. The vast majority of patients with pancreatic cancer are presently diagnosed at a late stage when the tumor has already extended outside of the capsule to invade surrounding organs and/or has metastasized extensively. Gold et al., Crit. Rev. Oncology/Hematology, 39:147-54 (2001). Late detection of the disease is common, and early pancreatic cancer diagnosis is rare in the clinical setting. This is significant, since late detection of pancreatic cancer results in low survival rate.
Current treatment procedures available for pancreatic cancer have not led to a cure, or to a substantially improved survival time. Surgical resection has been the only modality that offers a chance at survival. However, due to a large tumor burden, only 10% to 25% of patients are candidates for “curative resection.” For those patients undergoing a surgical treatment, the five-year survival rate is still poor, averaging only about 10%.
Early detection and diagnosis of pancreatic cancer, as well as appropriate staging of the disease, would provide an increased survival advantage. A number of laboratories have attempted to develop a diagnostic procedure based upon the release of a tumor-associated marker into the bloodstream, as well as detection of the marker substance within biopsy specimens. The best previously-characterized tumor associated marker for pancreatic cancer has been the immunoassay for CA19.9. Elevated levels of this sialylated Lea epitope structure were found in 70% of pancreatic cancer patients but were not found in any of the focal pancreatitis specimens examined. However, CA19.9 levels were found to be elevated in a number of other malignant and benign conditions, and currently the assay cannot be used for diagnosis. The assay is useful for monitoring, with continued increase in CA19.9 serum levels after surgery being indicative of a poor prognosis. Many other monoclonal antibodies (MAbs) have been reported with immunoassays for diagnosis in varying stages of development. These include but are not limited to DUPAN2, SPAN1, B72.3, Ia3, and various anti-CEA (carcinoembryonic antigen, or CEACAM5) antibodies.
Antibodies, in particular MAbs and engineered antibodies or antibody fragments, have been tested widely and shown to be of value in detection and treatment of various human disorders, including cancers, autoimmune diseases, infectious diseases, inflammatory diseases, and cardiovascular diseases [Filpula and McGuire, Exp. Opin. Ther. Patents (1999) 9: 231-245]. The clinical utility of an antibody or an antibody-derived agent is primarily dependent on its ability to bind to a specific targeted antigen associated with a particular disorder. Selectivity is valuable for delivering a diagnostic or therapeutic agent, such as drugs, toxins, cytokines, hormones, hormone antagonists, enzymes, enzyme inhibitors, oligonucleotides, growth factors, radionuclides, angiogenesis inhibitors or metals, to a target location during the detection and treatment phases of a human disorder, particularly if the diagnostic or therapeutic agent is toxic to normal tissue in the body. Radiolabeled antibodies have been used with some success in numerous malignancies, including ovarian cancer, colon cancer, medullary thyroid cancer, and lymphomas. This technology may also prove useful for pancreatic cancer. However, previously reported antibodies against pancreatic cancer antigens have not been successfully employed to date for the effective therapy or early detection and/or diagnosis of pancreatic cancer.
There remains a need in the art for antibodies that exhibit high selectivity for pancreatic cancer and other types of cancers, compared to normal pancreatic tissues and other normal tissues. In particular, there remains a need for antibodies that perform as a useful diagnostic and/or therapeutic tool for pancreatic cancer, preferably at the earliest stages of the disease, and that exhibit enhanced uptake at targeted antigens, decreased binding to constituents in the blood of healthy individuals and thereby also optimal protection of normal tissues and cells from toxic therapeutic agents when these are conjugated to such antibodies. Use of such antibodies to detect pancreatic cancer-associated antigens in body fluids, particularly blood, can enable improved earlier diagnosis of this disease, so long as it differentiates well from benign diseases, and can also be used for monitoring response to therapy and potentially also to enhance prognosis by indicating disease burden.